Nanomaterials and process for making the same

ABSTRACT

Process for producing nanomaterials such as graphenes, graphene composites, magnesium oxide, magnesium hydroxides and other nanomaterials by high heat vaporization and rapid cooling. In some of the preferred embodiments, the high heat is produced by an oxidation-reduction reaction of carbon dioxide and magnesium as the primary reactants, although additional materials such as reaction catalysts, control agents, or composite materials can be included in the reaction, if desired. The reaction also produces nanomaterials from a variety of other input materials, and by varying the process parameters, the type and morphology of the carbon nanoproducts and other nanoproducts can be controlled. The reaction products include novel nanocrystals of MgO (percilase) and MgAl 2 O 4  (spinels) as well as composites of these nanocrystals with multiple layers of graphene deposited on or intercalated with them.

RELATED APPLICATIONS

This is a continuation-in-Part of application Ser. No. 13/237,766, filedSep. 20, 2011, which is a continuation-in-part of application Ser. No.13/090,053, filed Apr. 19, 2011, now U.S. Pat. No. 8,377,408.

BACKGROUND OF THE INVENTION

1. Field of Invention

This invention pertains generally to carbon graphenes and othernanomaterials and to a process for making the same.

2. Related Art

Nanomaterials is an emerging new field to which major efforts inresearch and development are being applied. The characteristics ofnanomaterials can differ significantly from those of conventionalmaterials in a number of respects that may be important to applicationsin many fields, including the medical field, semiconductors, energystorage, advanced composites, electronics, and catalytics. Manynanomaterials can be used in ways that exploit their quantum-mechanicalproperties.

Recently, significant research and interest have been focused ongraphenes. Graphenes are allotropes of carbon in the form of one atomthick sheets of carbon atoms densely packed in a hexagonal honeycombcrystal lattice. Graphenes have a number of unique and desirablequalities, including extraordinary surface area, electrical conductivityand capacitance, thermal and mass transfer capability, magneticproperties, and extraordinary values of tensile strength and modulus ofelasticity. These attributes, individually or in combination, areprojected to make carbon graphene structures applicable to a number ofimportant technologies and markets, including electrolytic storage mediafor lithium ion batteries and ultra capacitors, facilitated transportmembranes for micro filtration, catalysis as substrate material, heattransfer for light-emitting diodes (LEDs) and other applications, highfrequency semiconductors for computing, hydrogen storage, conductivematerials for flatscreen and liquid crystal displays (LCDs), andstrengthening agents for advanced materials in wind turbines andautomobiles. IBM has demonstrated a 100 gigahertz graphene transistorand stated that a 1 terahertz transistor graphene is conceivable.

There are a number of known methods for producing graphenes, includingchemical vapor deposition, epitaxial growth, micro-mechanicalexfoliation of graphite, epitaxial growth on an electrically insulatingsurface, colloidal suspension, graphite oxide reduction, growth frommetal-carbon melts, pyrolysis of sodium ethoxide, and from nanotubes.Each of these methods has well documented advantages and disadvantages.A general advantage of many of the processes is the ability to producerelatively pure graphene materials and, in some cases, large continuoussurface graphene materials. Processes such as epitaxial growth andcolloidal suspension may lead to the customization of graphene materialsto suit very specific requirements.

There are also a number of known methods for producing other forms ofcarbon nanomaterials such as nanospheres, fullerenes, scrolls andnanotubes, including, for example, the use of carbon arc and lasertechnologies.

To date, however, no process for the production of carbon nanomaterialshas been successfully commercialized, despite many serious efforts to doso, particularly with respect to carbon nanotubes. Therefore, there isjustified concern that commercial production of graphenes may also bedifficult to realize. All the known graphene formation processes havesignificant limitations and disadvantages, including the dependency onrelatively scarce highly crystalline graphite as feedstock, high cost,and limited scalability. Because of these limitations, the known methodsmay not be capable of providing a dependable supply of low costgraphenes with high volumes of production.

The invention is based upon an extremely robust and scalable reaction inwhich the preferred reagents or feedstock are carbon dioxide (CO₂) andmagnesium (Mg).

When carbon-based fuels such as coal, oil, and natural gas are variouslycombusted to generate heat, substantial amounts of CO₂ and othercombustion products are produced, and there is widespread concern aboutthe historically high and increasing amounts of CO₂ in the atmosphere.Scientists believe the unusually high levels of CO₂ in the atmospherecould cause or are already causing adverse global climate effects andacidification of the oceans. While a number of solutions have beenproposed for the reduction of CO₂ emissions, the dominant model inpublications and public policy debate involves capture of the CO₂ by oneor another of several chemical mechanisms, followed by compression ofthe captured CO₂ and, finally, disposition of the CO₂ as a waste productby injection (sequestration) into the earth. Since the capture of CO₂from fossil fuel emissions is costly and energy intensive, it would bedesirable if at least some of the captured CO₂ be put to productive userather than be treated as a waste product. An economically feasible,large scale, and profitable process for reduction of CO₂ to carbonproducts would create demand for captured CO₂ and reduce the requirementfor sequestration of CO₂.

There are a number of known methods for the reduction of CO₂. One suchprocess is photosynthesis, which is a widely appreciated and prolificCO₂ reduction mechanism that reduces CO₂ to carbon that is then used bythe living system to produce complex organic molecules which arenecessary for life. However, photosynthesis has the disadvantage ofbeing difficult to replicate in technical or man-made biologic systems.

Ferrous Oxides, including magnetite and several other similar mineralcompounds, have also been found to beneficially reduce CO₂ to anamorphous form of carbon. Likewise, liquid potassium has been found tobeneficially reduce CO₂ to amorphous carbon. In addition, there are anumber of partial reduction (mineralization) processes in which CO₂ isconverted to carbonates. Partial reduction approaches are currentlyconsidered more likely than full reduction of CO₂ to carbon to befeasible alternatives to sequestration because full reduction of CO₂ isgenerally believed to be steeply endothermic and, therefore,economically challenging. However, partial reduction approaches have thedisadvantage of producing materials for which the market prices arerelatively low.

In sum, previously known CO₂ reduction methods are limited practicallyand economically by one or more factors, including cumbersome mass flowrequirements, significant energy requirements, high cost of reactants,difficult or risky materials management, and/or low value of the endproducts, with the value of the products often being less than the costof producing them.

Magnesium is not presently found in nature in pure form and must beproduced by one or more well-known methods from one or more of itsnatural existing forms, which include magnesium chloride and magnesiumoxide. Magnesium is frequently produced from seawater where it residesnaturally as the second most abundant cation. In this productionprocess, the Mg is precipitated with calcium hydroxide, and theprecipitant is reacted with HCl and finally reduced to magnesium byelectrolysis.

Other processes, including the Pidgeon process, which utilize heat toreduce mined magnesium rich ore, are employed to produce relatively puremagnesium. However, these processes are relatively expensive and do notalways produce the level of purity desired.

OBJECTS AND SUMMARY OF THE INVENTION

It is, in general, an object of the invention to provide new andimproved carbon graphenes and other nanomaterials and a new and improvedprocess for making the same.

Another object of the invention is to provide nanomaterials and aprocess of the above character which overcome the limitations anddisadvantages of the prior art.

These and other objects are achieved in accordance with the invention bycombusting reactants together in a highly exothermic oxidation-reductionreaction which produces high energy and heat at a temperature ofapproximately 5610° F., or higher, then rapidly cooling products of thereaction to form nanoparticles, and then separating nanoparticles ofdifferent materials from each other.

In some of the preferred embodiments, the high heat is produced by anoxidation-reduction reaction of carbon dioxide and magnesium as theprimary reactants. Additional materials such as reaction catalysts,control agents, or composite materials can be included in the reaction,as desired. The reaction is capable of producing nanomaterials from avariety of input materials. The carbon dioxide and magnesium arecombusted together in a reactor to produce nano-magnesium oxide,graphenes, graphene composites, and, if desired, other nanoproductswhich are then separated or excluded by suitable processes or reactionsto provide the individual reaction products.

By varying the process parameters, such as reaction temperature andpressure, the type and morphology of the carbon nanoproducts and othernanoproducts can be controlled.

The Mg—CO₂ reaction is highly energetic, producing very high temperatureon the order of 5610° F. (3098° C.), or higher, and also produces largeamounts of useful energy in the form of heat and light, includinginfrared and ultraviolet radiation, all of which can be captured andreused in the invention or utilized in other applications. The productsof combustion, particularly the magnesium oxide, can be recycled toprovide additional oxidizing agents for combustion with the carbondioxide.

The reaction products include novel nanocrystals of MgO (periclase) andMgAl₂O₄ (spinels) as well as composites of these nanocrystals withmultiple layers of graphene deposited on or intercalated with them.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of one embodiment of a process for theproduction of carbon graphenes and other nanomaterials in accordancewith the invention.

FIG. 2 is a flow diagram of another embodiment of a process for theproduction of carbon graphenes and other nanomaterials in accordancewith the invention.

FIG. 3 is a vertical sectional view of one embodiment of a reactor forcarrying out the process of the invention.

FIG. 4 is a vertical sectional view of the reaction chamber in theembodiment of FIG. 3 operating as a continuous annular flow combustor.

FIG. 5 is a vertical sectional view of the reaction chamber in theembodiment of FIG. 3 operating as a centrifugal separator.

FIG. 6 is a block diagram of one embodiment of a system for carrying outthe process of the invention.

FIG. 7 is a block diagram of another embodiment of a system for carryingout the process of the invention.

FIG. 8 is an exploded vertical sectional view of one embodiment of ahigh pressure CO2 reactor or furnace suitable for use in the embodimentof FIG. 7

FIG. 9 is a bottom plan view of the upper end cap of the reactor in theembodiment of FIG. 8.

FIG. 10 is a top plan view of the lower end cap of the reactor in theembodiment of FIG. 8.

FIG. 11 is a block diagram of another embodiment of a system forcarrying out the process of the invention.

FIG. 12 is a vertical sectional view, partly schematic, of anotherembodiment of a reactor for use in carrying out the process of theinvention.

FIG. 13 is an enlarged bottom plan view of the lower wall of thereaction chamber in the embodiment of FIG. 12.

FIG. 14 is a vertical sectional view, partly schematic, of anotherembodiment of a reactor for use in carrying out the process of theinvention.

FIG. 15 is a vertical sectional view, partly schematic, of anotherembodiment of a reactor for use in carrying out the process of theinvention.

FIG. 16 is a cross-sectional view taken along line 16-16 in FIG. 15.

FIG. 17 is a flow chart showing the conversion of MgO to Mg byelectrolytic reduction in one embodiment of the invention.

FIG. 18 is a transmission electron microscopy (TEM) bright field imageof a material having graphene platelets and graphene-MgO compositesproduced in accordance with the invention.

FIG. 19 is a TEM image of graphene-MgO crystal with layers of grapheneproduced in accordance with the invention.

FIG. 20 is a TEM image of crystals of magnesium oxide (periclase)produced by the process of the invention.

FIG. 21 is a scanning electron microscopy (SEM) image of magnesium oxide(periclase) cubic nanocrystals produced by the process of the invention.

FIG. 22 a is a TEM image of a graphene sample generated with solid CO2(dry ice) on a 20 nanometer scale.

FIG. 22 b is a TEM image of a graphene sample generated with solid CO2(dry ice) on a 10 nanometer scale.

FIG. 22 c is a TEM image of a graphene sample generated with gaseous CO2on a 20 nanometer scale.

FIG. 23 a is a TEM image of graphene platelets formed on an MgOsubstrate on a 100 nanometer scale.

FIG. 23 b is a TEM image of a portion of the graphene platelets of FIG.23 a on an enlarged (20 nanometer) scale.

DETAILED DESCRIPTION Overview

In the invention, an oxidizing agent such as CO₂ is combusted with areducing agent such as magnesium in a high temperature reactor to formvarious nanoscale products such as graphenes, graphene composites, MgO,and other nanomaterials. Thus, as illustrated in FIG. 1, the CO₂ andmagnesium are introduced into a reactor where a combustion reactionoccurs, producing a heterogeneous mixture of nanoscale materialsconsisting primarily of carbon and MgO nanoparticles. The reactionproduces intense amounts of energy including heat at a temperature of5610° F. (3098° C.), or higher, infrared radiation, visible light, andultraviolet electromagnetic radiation, all of which can be captured andutilized. The carbon and magnesium oxide are then separated from eachother and from any other reaction products that may be present in anintegrated set of process steps such as annular flow separation, cycloneseparation, gravity cell separation, flotation separation, centrifugalseparation, acid washing, deionized water washing, ultrasonicprocessing, elevated temperature treatment in a vacuum, and/or othersuitable separation processes. The heat produced by the reaction isrecovered for use in the separation steps and in purifying the reactionproducts, and the UV radiation and other energy produced by the reactioncan be recovered for other uses. The chemistry, temperature of reaction,rate of cooling, pressure, input materials and gases and otherparameters are controlled to determine the quality, character andmorphology of the reaction products. All or part of the MgO product isrecycled to provide highly purified magnesium for use in the reaction.

The products produced by the invention are determined by the control ofvariables in all phases of the process, i.e. pre-reaction, during thereaction, and post reaction. For example, the introduction of additionalmaterials to the reaction has been found to result in the production ofnano-forms and composites of the added materials, varying the reactiontemperature and gradient has been found to influence the morphology ofthe reaction products, and varying the separation and purificationtreatment has been demonstrated to significantly alter the constituencyof the products.

The invention has been found to produce a novel intercalated ormultilayered graphene-magnesium oxide composite as well as nanoscale MgOparticles in various forms, including periclase, or crystalline MgO.Other materials present in the reaction can also be converted tonanomaterials or composites. For example, when aluminum is present as analloy material in the magnesium, the invention produces nano-spinels(crystalline MgAl₂O₄). Other oxidizing agents can be introduced to thereaction as inputs with the feedstock to produce new composite orsingle-component nanostructures. In addition, non-reactant materialssuch as silicon, silver, gold, copper, and iron can be introduced intothe reaction to produce nano forms of those materials, graphenesdecorated with those materials, and graphene composites and other nanocomposites of them.

The magnesium-CO₂ reaction is highly exothermic and produces a highenergy flux across the electromagnetic spectrum, including very hightemperature in the range of 5610° F. (3098° C.). The invention includesprocess controls and systems for preserving the intense energy of thereaction, including management, capture, and reuse that energy toimprove the operational and economic efficiency of the process. The heatfrom reaction can be used for product separation and purification and inconverting the MgO to magnesium for recycling in the process, or forsale for use in the production of electricity or for other uses.Ultraviolet energy produced by the reaction is also captured and used.

Recycling most or all of the MgO product for use in the reaction notonly keeps the cost of the feedstock down, but also minimizes impact onthe market for magnesium, particularly when the invention is operated atlarge scale. It is also significant in view of the limited capacity toproduce magnesium from mined sources. In one presently preferredembodiment, for example, the MgO product is reduced to magnesium byelectrolysis, which is a relatively low-cost, energy efficient processcompared to conventional techniques for producing magnesium.

The products of the invention include nanoscale materials such as carbongraphenes and MgO nanoparticles and, if desired, novel graphenecomposites and other nanomaterials. The invention can also producenon-carbon nanomaterials such as spinels and novel intercalated orlayered graphene-periclase and graphene-spinel composite materials, andit is believed to be capable of producing many other forms ofnanomaterial as well. In addition, as noted above, non-reactivesubstances such as silver or silicon can be introduced to the reactionto produce nano-silver, nano-silicon, silver or silicon decoratedgraphenes, silver- or silicon-graphene composites, and other silver orsilicon nano composites. Two forms of nanocrystals produced by theinvention are spinels (crystalline MgAl₂O₄) and periclase (crystallineMgO). In addition, composites of these nanocrystals with multiple layersof graphene deposited on them or intercalated with them have also beenproduced. In such composites, the layers are in the range of onenanometer or less apart and are held together by Van der Waals forces.The graphene-periclase and graphene-spinel nano-composites are believedto be novel materials.

While the exothermic reaction of CO₂ and magnesium is utilized in thepreferred embodiment, the heat can be supplied by other sources such asother exothermic chemical reactions, a high temperature nuclear reactor,a solar furnace, an electric arc, magneto hydrodynamic heating ofplasma, combustion of hydrogen or other fuel, or by other suitablemeans. Likewise, the initial reactant for producing graphenes can be anycarbon containing molecule such as carbon dioxide, carbon monoxide,phosgene (COCl₂), methane, ethylene, acetylene, other carbon containingmaterial, and combinations thereof. Similarly, other earth metals suchas aluminum, titanium, zinc, sodium, lithium, calcium, and combinationsthereof can be used as the reducing agent.

Preferred Embodiments

In the embodiment illustrated in FIG. 2, CO₂ and magnesium areintroduced into a high temperature reactor 21 where they are combustedtogether in a highly exothermic oxidation-reduction reaction whichproduces high energy and heat at a temperature on the order of 5610° F.(3098° C.), or higher, while producing a homogeneous reaction productconsisting of magnesium oxide (MgO) and carbon in accordance with therelationship:2Mg(s)+CO₂(g)→2MgO(s)+C(s).

The homogeneous reaction product is cooled rapidly by beneficialexpansion of the superheated reaction products or by additional activecooling to quench and retain the nanoparticle structure and then wettedin a bath of deionized water 22. This results in the wetting of thenanocarbon graphene and nano MgO reaction products, with some of the MgOreacting with the water to form magnesium hydroxide (Mg(OH₂)):MgO(s)+H₂O(l)→Mg(OH)₂.

The mixture is then treated with an ultrasonic probe 23, operating, forexample, at a frequency of 20 kilohertz and a power level of 500 watts,to break up the heterogeneous reaction product into smaller particles,exposing more surface area for subsequent treatment or processing.

Hydrochloric acid (HCl) 24 is added to the ultrasonically treatedmixture. The carbon graphenes are inert to HCl, but the HCl reacts withunreacted magnesium in the mixture as well as the dissolved MgO andMg(OH₂) to form magnesium chloride (MgCl₂) and water (H₂O):Mg(OH)₂(s)+2HCl(l)→MgCl₂(s)+2H₂O(l).

After the reaction products have been treated with HCl, the solution isfiltered using a Büchner vacuum funnel 26 with 2.5 micron filter paper,with the graphenes being deposited onto the filter paper and the MgCl₂passing through. The filter paper and graphenes are then heated, in afirst heating stage 27, to a temperature of 93° C. to dry the graphenesand facilitate their removal from the filter paper.

In order to fully remove any oxide attached to or co-mingled with thegraphenes, the graphenes are placed in a seasoned quartz boat and heatedin a seasoned quartz tube oven 28 under vacuum at a temperature of 1150°C. for a predetermined time. This step is repeated until the grapheneshave reached a desired level of purity, with successive repetitionsproviding a linear reduction in the magnesium contamination of thegraphene product.

The MgCl₂ from filter 26 is processed by electrolysis in a cell 29 toseparate the magnesium from the chlorine:MgCl₂(s)+Energy→Mg(s)+Cl₂(g).

The magnesium is recycled to reactor 21 for use in the Mg—CO₂ reaction,and the chlorine can be recycled or sold.

Magnesium oxide vented from the reactor is captured and processed byfiltration 30 to recover MgO nanoparticles.

The reaction is preferably carried out in a heavily insulated,externally cooled reactor, one embodiment of which is shown in FIG. 3.This reactor has an upright, open-ended reaction chamber 31 with aninner cylindrical side wall 32, an outer side wall 33, insulation 34between the walls, and a floor 36. The inner wall is a double wallstructure with an inner layer or section 32 a fabricated of a materialthat will withstand reaction temperatures on the order of 5610° F.(3098° C.) or higher and not introduce impurities into the reaction andan outer layer or section 32 b fabricated of an insulative material thatcan also withstand the high temperatures produced by the reaction. Theinner layer or section can, for example, be fabricated of a mixture ofzirconia and rare earth oxides, graphite, or another suitable materialthat is compatible with high temperatures. Outer wall 33 is fabricatedof metal and is liquid-cooled to lower the local temperature and collectwaste heat. Ports such as inlet ports 37, 37 provide communication withthe interior of the reaction chamber and permit a controlledintroduction of feedstock or reagents, inert gases, other materials andgases, and sensors into the reaction chamber. Other ports (not shown)provide a controlled withdrawal of a reaction product from the chamber.

The CO₂ atmosphere in the reactor provides an oxygen-free environmentthat prevents combustion of the graphene, other reaction products, andthe graphite reactor walls. At the outlet end of the open-ended reactor,the CO₂ gas zone allows the carbon products additional time to coolbelow ignition temperature. Magnesium metal particles for the reactioncan be injected into the reactor in an argon gas stream, and the argoncan also be used to provide a barrier to keep other potentially reactivegasses such as oxygen or nitrogen out of the combustion reaction.

The reactor can be operated either in a batch mode or in a continuousmode. Batch processing has been found to allow for significant controlof reaction parameters including, for example, time of reaction, and maybe preferable for certain end product objectives. However, a continuousprocess generally provides a larger product yield in a shorter period oftime and may, therefore, be the preferred mode in many applications.

In the batch mode, gaseous MgO is beneficially ejected from the reactionchamber, and the other reaction products are separated outside thechamber, with the reaction product entering the separation process as aheterogeneous mix, as in the embodiment of FIG. 2.

In the continuous mode, initial separation of the reaction productsoccurs in the reaction chamber, as seen, for example, in FIG. 4. Here,the reactor is shown as operating as a continuous annular flowcombustor, with initial separation of the carbon and magnesium oxidereaction products occurring in an annular flow process. In thisembodiment, CO₂ gas and solid magnesium particles are fed into the lowerportion of the chamber and ignited with an electric arc or ahydrogen-oxygen flame to produce an upwardly directed annular flow offluidized CO₂, magnesium oxide, and reaction particles, with a highdensity annular flow component 39 in the outer portion of the chamberand a lower density annular flow component 41 in the inner region. Asthe flow progresses upwardly, the inner region and the boundary betweenthe two regions expand outwardly, with the particles of greater densitybeing concentrated near the side wall of the chamber toward the top ofthe reaction zone. Although the reactor is shown with a verticalorientation and an upward flow, the reactor can be inverted and have theflow in a downward direction, or it can be oriented horizontally andhave a horizontal flow, if desired.

Ignition of the CO₂ and Mg is initiated by the electric arc or flame atthe base of the reaction chamber, and the conical shape of the innerflow zone results from the action of the particles in the Mg—CO₂reaction. Thus, as noted above, there is an upward flow of high density,heated nanocarbon and magnesium oxide particles in the outer portion ofthe chamber and an upward flow of low density, heated nano-carbon andmagnesium oxide particles in the inner region, with the inner regionexpanding outwardly as the flows progress upwardly. As the reactionproducts travel upward through the annular flow zone, they also mayacquire a rotational component of velocity either naturally or fromfixed vanes that further aid in the separation process. Thus, asillustrated, the upward flow of high density, low rotational velocity,lower temperature nano-carbon particles and magnesium oxide particlesoccurs in the outer portion of the chamber, while the upward flow ofhigh rotational velocity, low density, very hot nano carbon particlesand magnesium oxide particles occurs in the innermost region. The lengthor height of the reaction chamber is sufficient to allow cooling of theC/Mg material before it leaves the reactor.

The result is an initial stage separation process integrated within thereactor that aids in separation of fluids or slurries as a function offluid density. The MgO vapor beneficially rises to the top of thechamber and can be collected, for example, with a partial vacuum, acooling system, and a receptacle. Vent ports at the top of the reactionchamber can be utilized to further facilitate the beneficial collectionof pure MgO. After leaving the reaction chamber, the reaction productsare further separated and treated to further prepare them for sale andrecycling. Management and control of the temperature, locus and durationof the reaction will determine the final composition of the materialsproduced by the reactor combustion process.

Rotating the reaction chamber about its central axis 42, as illustratedin FIG. 5, provides centrifugal separation of the reaction products asthey flow upwardly through the reaction zone. In the lower region 43 ofthe zone, there is an upward flow and flux of carbon nanoparticles, MgO,and other reaction products at relatively low rotational velocity andtemperature, with higher and lower density particles interspersed bothin the inner portion 41 and in the outer portion 39 of the region. Bythe time the particles reach upper region 44 of the chamber, they haveacquired a much higher rotational velocity, and they are very hot, withthe particles of higher density being concentrated in the outer regionnear side wall 32 and the particles of lower density in the innerregion.

In the batch process illustrated in FIG. 6, CO₂ and magnesium areintroduced into a reactor furnace 46 where they are combusted togetherin a highly exothermic oxidation-reduction reaction, as discussed above,producing a mixture of carbon and magnesium oxide (MgO) products whichare delivered to a preparation stage 47 where they are ground into finerparticles and prepared for further processing. These particles areprocessed ultrasonically in deionized water in a sonifier 48, thenwashed in hydrochloric acid (HCl). The carbon graphenes are inert toHCl, but the HCl reacts with unreacted magnesium in the mixture as wellas the dissolved MgO and Mg(OH₂) to form magnesium chloride (MgCl₂) andwater (H₂O).

The aqueous solution of carbon graphenes and MgCl₂ is filtered in avacuum filter 49 to separate the graphenes from the MgCl₂. The graphenesare dried in a dryer 51 and recycled back through the sonification,filter, dryer, and heating stages to further purify them. The number oftimes the graphenes are recycled is determined by the level of puritydesired, and is typically on the order of three or four times per cyclebatch. When the purification process is completed, the graphenes aredischarged through a product line 52.

Magnesium oxide (MgO) produced by the Mg—CO₂ reaction is collected andconverted to magnesium which is recycled for use in the reaction. Thus,gaseous MgO from the reactor is collected and solidified in a collector53, then washed with HCl and converted to MgCl₂ in a dissolver 54. ThisMgCl₂ is dried in a dryer 55 along with the MgCl₂ that was separatedfrom the carbon graphenes in filter 49. The dried MgCl₂ is thenseparated into magnesium and chlorine by electrolysis in a cell 56. Themagnesium is cooled in a cooler 57, then collected and ground into finerparticles, e.g. 400 Mesh, in a collector and grinder 58. The magnesiumparticles from the grinder are fed back to reactor 46 and used in thecombustion process. Although grinding is used in this particularembodiment, the magnesium can also be reduced to finer particles byother means such as cutting or cooling small droplets from a melt.

In addition to the reaction products, the combustion of CO₂ andmagnesium also produces substantial amounts of heat and energy which arecaptured and utilized in other steps of the process, such assonification and drying, or otherwise.

Chlorine, hydrogen, and HCl utilized in the process are provided by acell 59 to which hydrogen (H₂) and methane (CH₄) are supplied along withthe chlorine from electrolysis cell 56.

FIG. 7 illustrates another embodiment of a batch process in whichignition of the CO₂ and magnesium is initiated by a hydrogen-oxygenflame. The hydrogen and oxygen are supplied to a reactor 61 throughbranches 62, 63, each of which includes a shut-off valve 64, a pressurereducing valve 66, a check valve 67, and an electrically operatedcontrol valve 68, designated prime in branch 62 and double prime inbranch 63. Pressure in the branch lines is monitored by pressuretransducers 69′, 69″. Hydrogen and oxygen from the branches are mixedtogether in and delivered to the reactor by a feed line 71 with a checkvalve 72 in the feed line to prevent backflow from the reactor to thebranches. A high voltage spark igniter 73 for the hydrogen-oxygenmixture is located at the base of the reactor.

Means is provided for supplying CO₂ to the reactor at a reduced pressurelevel until ignition occurs and thereafter at higher pressure. Thismeans includes a low pressure branch 76 and a high pressure branch 77.The low pressure branch has a pressure reducing valve 78, a flow controlvalve 79, and a check valve 81, with a flowmeter 82 and a pressuretransducer 83 for monitoring flow and pressure in the branch. The highpressure branch has a control valve 84. CO₂ is supplied to the twobranches through a supply line 85 with a shut-off valve 86 and apressure transducer 87. CO₂ from the branches is supplied to the reactorthrough a feed line 88, with a pressure transducer 89 for monitoring thepressure of the CO₂ in that line.

Reactor 61 has a removable cap or lid 61 a, and the magnesium particlesto be combusted are poured directly into the reactor when the lid is offand the reactor is not operating.

A discharge line 91 is connected to the reactor for collecting theproducts of the reaction, with a control valve 92 for controllingproduct discharge and a pressure relief valve 93 through which gaseousproducts of combustion can escape in the event that the pressure in thereactor becomes too high.

A vacuum system 94 is also connected to the reactor for collecting MgOparticles produced by the combustion of CO₂ and magnesium. A controlvalve 96 is included in the line 97 between the reactor and thecollector, and a pressure transducer 98 monitors the pressure in theline.

Data from the pressure transducers and flowmeter is delivered to a dataacquisition and control system 99 which processes the data and controlsthe operation of the control valves and the igniter.

To begin the process, the lid is removed from the reactor, and the Mgparticles are poured into the chamber. The lid is replaced, and controlvalve 79 is opened to allow CO₂ to flow into the reactor at the reducedpressure set by regulator valve 78. Control valves 68′, 68″ are alsoopened to allow hydrogen and oxygen to flow into the reactor, andigniter 73 is turned on to ignite those gases. The hydrogen-oxygen flameignites the Mg particles and the CO₂, and when they begin to burnvigorously, control valves 68′, 68″ are closed to shut off the flow ofhydrogen and oxygen. At the same time, control valve 84 is opened todeliver the high pressure CO₂ to the reaction chamber, and valve 79 isclosed to shut off the low pressure flow. As the reaction progresses,control valve 92 is opened to allow the discharge and collection of thereaction products through discharge line 91, and control valve 97 isopened to allow vacuum system 96 to draw gaseous MgO into the vacuumcollector where the MgO particles are collected.

One embodiment of a high pressure CO₂ reactor or furnace suitable foruse in the process of FIG. 7 is illustrated in FIGS. 8-10. This reactorhas a cylindrical side wall 101 with end caps 102, 103 threadedlyattached to the upper and lower end portions of the side wall to form aclosed chamber 104. They are fabricated of a material that can withstandthe extremely high temperatures of the reaction, and in the embodimentillustrated, they consist of a carbon steel pipe nipple and a pair ofcarbon steel pipe caps, with the length of the nipple and the outerdiameter of the caps both being on the order of 5 inches.

A reactor bed 106 is provided in the bottom wall 103 a of lower end cap103. This bed consists of a ¼ inch deep pocket 107 formed in one half ofthe bottom wall filled with a material 108 such as zirconium dioxide(ZrO₂) or zirconia which can withstand the high temperatures and notintroduce impurities into the reaction.

Ports are formed in the end caps to provide communication with thereactor chamber when the reactor is in use. The ports include an H₂/O₂inlet port 109 and an ignition port 111 in the side wall 103 b of thelower end cap, a CO₂ inlet port 112 in the upper wall 102 a of the topcap, a product outlet port 113 in upper wall 102 a for the carbon andmagnesium reaction products, and another outlet port 114 in the upperwall for the gaseous MgO. These ports are threaded for connection to thelines that carry the incoming gases, the ignition conductor, and thereaction products. Clearance holes 116, 117 are formed in side wall 101in registration with inlet port 109 and ignition port 111 in the sidewall of the lower cap. In this particular embodiment, there is no portfor the magnesium since it is introduced by removing the top cap andpouring the magnesium particles onto the reactor bed.

FIG. 11 illustrates an embodiment in which ignition of the CO₂ andmagnesium is initiated by an electric arc. In this embodiment, CO₂ issupplied to reactor 118 at ambient pressure through a supply line 119which includes a shut-off valve 121, a pressure reducing valve 122, acontrol valve 123, and a check valve 124, with pressure transducers 125,126 and a flowmeter 127 for monitoring pressure and flow in the line.The reactor walls and lid are fabricated of a material, such as carbonsteel, that is capable of withstanding the high temperatures produced bythe reaction, and a graphite crucible 128 is disposed within thereaction chamber for holding the magnesium particles for combustion.Those particles are introduced by removing the lid and pouring them intothe crucible. Temperature and pressure within the reactor are monitoredby a thermocouple 129 and a pressure transducer 131.

The arc for initiating ignition of the CO₂ and magnesium is provided byan electric arc generator 132 which can, for example, be similar to thatemployed in an arc welder and have a rating on the order of 90 amperesat 40 volts AC.

As in the embodiment of FIG. 6, the reaction products are collectedthrough a discharge line 133 which includes a control valve 134 and apressure relief valve 136, and MgO particles are collected in a vacuumcollector 137 which is connected to the reactor by an output line 138which includes a control valve 139 and a pressure transducer 141.

Data from the pressure transducers, flowmeter, and thermocouple isdelivered to a data acquisition and control system 142 which processesthe data and controls the operation of the control valves and the arcgenerator.

Care is taken to ensure the ejected reaction products, particularly thegraphenes, are not combusted post reaction by interaction of the carbonwith oxygen and high heat. The presence of a CO₂ or similarly inert gasat the reaction exit point is maintained and high heat is drawn awayfrom the exit point by an integrated cooling system.

The nanocarbon graphene and nano MgO reaction products have been foundto be extremely consistent from batch to batch in the embodiment of FIG.11. Also, with the gaseous CO₂ feedstock, this process has producedmeasurably and significantly less intercalated material, specificallyMgO encapsulated in graphene layers, than batch processes employingsolid CO₂ feedstock. Gaseous carbon monoxide (CO) was also investigatedas an alternative feedstock in this embodiment, but the CO—Mg reactionwas much less vigorous than the Mg—CO₂ reaction, probably due to thelesser amount of oxygen available to the reaction. CO may be useful inregulating the rate of the Mg—CO₂ reaction.

In the embodiment of FIG. 12, low pressure CO₂ gas is utilized in thereaction process. This embodiment includes a reaction chamber 143 with acylindrical side wall 144 and a bottom wall 146 fabricated of amaterial, such as carbon steel, which will withstand the hightemperatures of the reaction. The chamber is open at the top, and agraphite crucible 147 is disposed within the chamber for holdingmagnesium particles 148. CO₂ gas is introduced into the chamber atatmospheric pressure through ports in the chamber walls and passesthrough slotted openings 149, 151 in the bottom and side walls 147 a,147 b of the crucible.

A hood 152 is mounted on the upper portion of side wall 144 forcollecting magnesium oxide (MgO) produced by combustion of the CO₂ andmagnesium in the reaction chamber. The MgO is drawn into and through thehood by a vacuum-operated collector 153 connected to the discharge endof the hood, with a valve 154 at the discharge end for controlling whenthe vacuum system can draw the MgO into the collector. The hood can beremoved from the chamber to allow the magnesium particles to be pouredinto the crucible.

The embodiment shown in FIG. 14 is generally similar to the embodimentof FIG. 12, and like reference numerals designate corresponding elementsin the two. In the embodiment of FIG. 13, hood 152 is fabricated ofstainless steel and includes a cooling chamber 156 with a screw conveyor157 for cooling the MgO and facilitating the recovery of MgO particlesfrom the reactor. In the embodiment illustrated, fluid coolant iscirculated through the cooler to cool the MgO passing through it. Ifdesired, additional cooling can be provided by using an internallycooled feed screw in the conveyor.

FIG. 15 illustrates a continuous flow embodiment utilizing ahorizontally extending reactor 158 having a conical side wall 159, withthe axis of the reaction chamber 161 being inclined downwardly at anangle on the order of 10 degrees relative to the horizontal. The reactorhas an end wall 162 at the small end of the cone and is open at thelarge end. An input manifold or chamber 163 is formed between the endwall and a baffle plate 164. This plate is spaced inwardly from andgenerally parallel to the end wall and is peripherally attached to theconical side wall. The reactor walls and the baffle plate are all madeof graphite.

A generally U-shaped trough 166 extends in a downwardly inclined mannerbetween the baffle plate and the open or outer end of the reactionchamber on the inner side of the lower portion of side wall 159. Anopening 167 in the baffle plate at the upper or inner end of the troughprovides communication between the input manifold and the reactionchamber.

Magnesium particles and CO₂ gas are introduced into the input manifoldwhere they mix together before flowing through the opening in the baffleplate to the upper portion of the trough. Means such as a gas flame oran electric arc is provided for initiating ignition of the CO₂ andmagnesium in the upper portion of the trough, and an inert gas such asargon is introduced into the intake manifold to prevent backflow fromthe reaction chamber to the manifold.

A feed screw or auger 169 extends longitudinally within the trough forcarrying solid reaction products to the outer end of the reactionchamber. The lower or outer end portion of the feed screw is internallycooled to provide cooling for the carbon and other solid reactionproducts before they are discharged at the lower end of the trough.

A significant portion of the magnesium oxide (MgO) gas and nanomaterialproduced by the Mg—CO₂ reaction beneficially rises to the top of thereaction chamber and passes through a cooling chamber 171 at the outerend of the upper portion of side wall 159 before being collected.

The system is maintained in an inert atmosphere to prevent post reactioncombustion of the carbon and other reaction products.

Another embodiment is a small to medium scale, self-contained,continuous flow system, referred to herein as the modular embodiment.The primary features of this embodiment include capture of CO₂ directlyfrom emissions, reduction of the CO₂ to carbon, production of reusablenanomaterials, and destruction, by heat of reaction, of harmful fossilfuel combustion products such as soot. The resultant nanocarbon, MgO,and other materials can be captured in a holding tank and separated inbatch mode on a regular basis. The modular embodiment can, for example,be utilized in the production of graphenes or other nanomaterials forindustrial purposes, and it may also be useful as a stationary emissionscontrol system on a ship or in conjunction with a stationary dieselgenerator. A smaller version may be useful in mobile vehicularapplications.

Subprocesses

A number of subprocesses are included in the preferred embodiments inorder to provide a complete system and process for the production ofnanomaterials. These subprocesses include management of reaction inputmaterials and ignition systems, reaction process controls, reactionproduct separation and purification treatment, integrated productfunctionalization, recycling of product materials, and energymanagement. These processes are an important part of the invention,enabling it to operate as an industrial system.

Materials Management

There are two primary inputs or feedstocks for the preferredreaction—CO₂ and magnesium. In the preferred embodiment, pure (99+%) orrelatively pure (commercial grade) gaseous CO₂ is utilized. If the CO₂gas contains or is seeded with other gases, these gases will, subject totheir inherent phase attributes, become an additional reaction productwith the MgO and graphenes. The CO₂ feedstock can be obtained in largevolumes from fossil fuel emissions, industrial sources such as breweriesand refineries, natural earth deposits and other sources. In thepreferred embodiments, the pressure of the CO₂ can be controlled toinfluence the performance of the reaction and the morphologies of theproducts, with CO₂ at a pressure in the range on the order of 200 to 800psi being preferred. The gaseous CO₂ is injected into the reactor at apressure determined to optimize the reaction performance and desiredproducts.

Magnesium can be obtained from third parties in various alloyed forms orin very pure form. In the preferred embodiments, pure (99+%) magnesiumfeedstock is utilized, and it is introduced in the form of smallparticles. The size of the particles has been found to have asignificant impact on the reaction and reaction products, and it isgenerally selected to achieve optimal reaction combustion and reactionproducts. The magnesium can, for example, be obtained in the form of barstock and machined to the desired particle size. Thin gauge magnesiumwire segments can also be used, if desired.

As discussed above, in the invention, a significant portion of themagnesium feedstock is obtained by recycling the very pure MgO productof the reaction in a low-cost electrolytic process. This method ofobtaining magnesium has several advantages, the first being that thecost of recycled magnesium will be much lower than the cost of magnesiummanufactured by third parties. A second advantage is that worldmagnesium production is relatively inelastic and, thus, magnesium couldbecome more expensive should operators of the invention requiresignificant amounts of fresh magnesium feedstock. Presently, more than80% of the world's magnesium supply is produced in China, whichsubsidizes the industry. Thus, the cost of magnesium may be artificiallylow, making recycling even more attractive. A third advantage ofrecycling is the high purity (more than 99%) of the recycled magnesium,which is important to the Mg—CO₂ reaction.

If desired, other oxidizing and/or reducing agents can be utilized inplace of or in addition to CO₂ and magnesium to produce other reactionproducts. The initial reactant for producing graphenes can be any carboncontaining molecule such as carbon dioxide, carbon monoxide, phosgene(COCl₂), methane, ethylene, acetylene, other carbon containing material,and combinations thereof. The reducing agent can be another earth metalsuch as aluminum, titanium, zinc, sodium, lithium, calcium, andcombinations thereof.

Ignition

High heat input is required for ignition of the Mg—CO₂ reaction. Tomaintain purity of the reaction products, it is preferable that anignition source not introduce foreign contaminants into the reactionchamber. The Mg—CO₂ mixture can, for example, be ignited with anelectric arc, an electric spark, a hydrogen-oxygen flame or a xenonlamp. An electric arc ignition with carbon electrodes is preferred dueto its ease of operation, ability to function continuously, ability tofunction in high temperature environments, and because it does notintroduce foreign material or gas to the reaction. Other ignitionsources may also be used as long as they impart no impurities into thereaction product.

Process Controls

Significant control of the reaction and reaction products is alsoprovided by manipulation of parameters such as regulation of thetemperature gradient, the contact and saturation of CO₂, and the natureand flow of the magnesium particles. In the preferred embodiments, anumber of process controls are implemented to optimize costs, safety,conservation of energy and materials, and production of desiredproducts. These controls include, but are not limited to, varying theattributes of or type of input materials and gases, controlling the heatof reaction, controlling speed of reaction, controlling thepost-reaction temperature gradient, controlling pressure within thereaction chamber, controlling the atmosphere into which the reactionproduct emerges to prevent combustion of the carbon, capturing theenergy released by the reaction, and controlling the post reactionproduct separation and treatment processes.

In the preferred embodiments, the feedstock is managed beforeintroduction to the reactor, and provisions are made in the reactordesign for the introduction of additional materials and gases. Thesupply, purity and pressure of CO₂ feedstock are managed, as are thesupply, purity and form of magnesium feedstock, with the size of themagnesium particles, and hence the volume to surface area ratio of themagnesium, directly impacting the production of and morphology of thereaction products. It has also been found that the amount of CO₂available to the reaction has a significant impact on the reactionproducts, and the CO₂ can be introduced at precisely controlledpressures and rates to control the reaction process and products. Anon-oxygen, CO₂, or inert gas environment is maintained post reactionand prior to heat dissipation to prevent combustion of the carbongraphenes. Solid particles of CO₂ may also be input into the reactor,depending on requirements, and will sublimate to large volumes of gas athigh pressures. In this manner, CO₂ can either be flooded at highpressure in the reactor, or it can be introduced in restrictivequantities which allow the operator to ‘throttle’ the reaction with theMg or Mg alloy or additional mixtures of input materials.

The reaction and reaction products can also be controlled by varying thepressure and presence of the gaseous and solid material inputs. Reactorsin which the invention is carried out are designed to accommodate theregulated introduction of a range of gaseous and solid material inputsother than the feedstock at all three stages of the reaction, i.e.pre-reaction, during the reaction, and post-reaction. Other reactivegases or inert gases, such as argon, can be introduced to furthercontrol and optimize the reaction process and products. Other reactivematerials such as aluminum, catalysts such as platinum, or non-reactivematerials such as silver or silicon can be introduced either with thefeedstock or directly into the reaction or at a point after thereaction. Also, the addition of non-reactant material with desirableattributes such as silver or silicon can result in the formation of acomposite or decorated graphene material with potentially advantageouscharacteristics.

It has also been found that controlling the temperature gradient towhich the vaporized reaction product and any additional materials areexposed immediately following the reaction affects formation of theproducts and the resultant morphologies and characteristics of thoseproducts. This gradient can be controlled in several ways. The reactorcan, for example, have an open configuration, or the reaction can beconfined to a limited space within the reactor. The use of an expanderand the presence of an inert or non-reactive gas between the reactionsite and the product outlet can also affect the temperature gradient,with the expander facilitating the natural tendency of hot vapor fromthe reaction to expand, cool, and nucleate or form the reaction product.A liquid or gaseous cooling agent can also be utilized to furthercontrol the temperature gradient in the reaction process. The coolingagent can, for example, be injected directly into the reaction chamber,the discharge region, or the expander, or it can be circulated in acooling jacket surrounding portions of the reactor.

Materials Separation

In both continuous flow and batch reactions, an initial separation ofreaction products occurs when gaseous MgO is vented beneficially awayfrom the other reaction products and/or when an upwardly directedannular flow process provides initial gravity separation of magnesiumoxide nanoparticles and carbon nanoparticles. The reaction products arethen further separated and purified in a post reaction separationprocess which is optimized for the production of the desired products.

In the preferred embodiments, the post reaction materials separationprocess consists of a substantially automated sequence of treatment,separation and purification steps which are applied to the unseparatedpost reaction product that emerges or is withdrawn from the reactor. Inthe production of graphenes and nano MgO, for example, the heterogeneousreaction product undergoes repeated cycles of treatment with deionizedwater, hydrochloric acid, and ultrasound, filtration to isolategraphenes, graphene drying, and heat treatment of the graphenes. Thiscycle is repeated as many times as needed to achieve the desired purityof graphenes.

Fluids are useful in separating materials that are resistant todissolution and have different specific gravities, and are required inultrasonic processing. In gravity separation and flotation, the densityof the solution within the cell is manipulated to a specific valuewhereby the particles sink or float to occupy distinct layers within thevessel. The fluid can be water or other substances such as acids orfluids with other densities, depending on the solubility and reactivityof the materials to be separated.

Magnesium Recycling

The recycling of magnesium is an important part of the invention becauseof the cost and difficulty of obtaining magnesium of high enough purityfor use in the Mg—CO₂ reaction, particularly in large scale operations.The crystalline nano MgO produced by the invention has been found to beextremely pure, and this unusually high purity makes recycling the MgOto Mg very practical and cost effective. Given the high cost ofmagnesium and MgO in the marketplace and the limited availability ofpure, non-alloyed magnesium, the ability to recover and recycle highlypure magnesium is an important element and advantage of the invention.

The preferred process for recycling magnesium in the invention iselectrolytic reduction from MgCl₂. The chemical and electrolytic stepsin the reduction of MgO to Mg by this process are shown in FIG. 17. Asillustrated, the MgO reaction product is converted to Mg(OH)₂ bytreatment with H₂O, and the Mg(OH)₂ is converted to MgCl₂ and H₂O bytreatment with HCl, with the differential thermal expansion between MgOand carbon opening up cracks in the carbon, allowing the HCl to attachto the carbon. In the electrolysis step, the MgCl₂ is separated intomagnesium nanoparticles and chlorine gas.

Energy Management and Reuse.

The invention is designed to preserve, capture and utilize as much ofthe exothermic energy of reaction as possible. The reaction temperatureof approximately 5610° F. (3098° C.) is unusually high and is in a rangethat can generally be achieved at larger scales only with solar furnacesor via nuclear reaction. In the preferred embodiments, waste heat fromthe reaction is captured and utilized in post reaction productseparation and treatment, including production of electricity for use inthe recycling of magnesium. Heat and light energy from the reaction canalso be captured and utilized in other applications.

Thermodynamic Analysis

A thermodynamic analysis of the Mg—CO₂ reaction and the recycling of theMgO reaction product is summarized in Table 1 below.

TABLE 1 Production of Solid Carbon through Reduction Of Gaseous CarbonDioxide with Magnesium Heat Heat (MJ/kg) (MJ/kg) Step ReactionThermicity Mg C. A Mg (s) + 0.5 CO₂ (g) → 1 MgO (s) + 0.5 C (s)Exothermic −16.8 −67.507 Production B MgO (s) + H₂O (l) → Mg(OH)₂Exothermic −3.37 −13.507 Mg Recycle C Mg(OH)₂ (s) + 2HCl (l) → MgCl₂(s) + 2H2O (l) Endothermic 5.74 22.993 Mg Recycle D MgCl₂ (s) + Energy →Mg (s)+ Cl₂ (g) Endothermic 22.4 89.667 Mg Recycle Total Endothermic7.91 31.647

As this table shows, one cycle of the process requires approximately 8MJ of energy for each kilogram of magnesium produced and approximately32 MJ for each kilogram of carbon. Each cycle generates 0.25 kg ofcarbon by reducing 0.92 kg of CO₂, and produces 1.45 kg of chlorine(Cl₂). On a molar basis, this can be expressed as:Mg(s)+H₂O(l)→Mg(OH)₂(s)+0.5C(s)+Cl₂,and on a mass basis as:1 kg Mg(s)+0.92 kg CO₂+0.75H₂O(l)+7.91 MJ→0.25 kg C(s)+1.45 kg Cl₂

The reactions were evaluated using a Gibbs free energy analysis thatprovides a theoretical maximum energy (heat) available for work in eachstep of the reactions. Steps A and B are exothermic, releasingapproximately 20 MJ of heat per kilogram of magnesium while recyclingSteps C and D are endothermic, requiring an energy input ofapproximately 28 MJ to proceed.

Example 1

A reactor was constructed using two blocks of solid CO₂, more commonlyknown as dry ice. A cavity was drilled in one of the dry ice blocks toserve as a reactor vessel, and the other block was used as a cover.Magnesium bar stock was machined into chips which were placed in thecavity and ignited with a propane torch, following which the cover blockwas immediately placed on top of the first block. The reaction product,a mixture of white and black crusty powder, was collected and sent outfor analytical testing. A second sample was prepared in a similar mannerand treated with deionized water and hydrochloric acid (HCl) beforebeing sent out for testing.

The test results showed that the reaction product consisted ofnanomaterial and that the nanomaterial consisted of two dominantmorphologies as well as some less frequently observed morphologies. Thetwo dominant morphologies were a clear, irregularly shaped, flatparticle showing classic evidence of graphitic (carbon) composition anda clear square, crystalline particle deduced to be MgO innano-crystalline (periclase) form. The untreated reaction product showedconsiderably more nano MgO than the sample that had been treated withdeionized water and HCl. The appearance of the carbon particles in eachsample was substantially the same.

This example shows that the Mg—CO₂ reaction, and most likely the energyfrom the reaction, causes the feedstock to vaporize and reform bynucleation as nanomaterial. The extreme temperature gradient between thereaction site or locus, where the temperature is approximately 5610° F.(3098° C.), and other locations within the reactor, where thetemperature is near ambient, is believed to cause very rapid reformationof solid material from the vaporous reaction product. Moreover, theextremely short time lapse from formation of the vaporous reactionproduct to ejection of the vapor from the reaction site and interactionwith the extreme temperature gradient surrounding the reaction sitelimits the operational timeframe for nucleation and results in theformation of very small, nanoscale particles. The reaction product vapornucleates and self-assembles as homogeneous bonded carbon and MgO.

The process described in this example is believed to be not just aprocess for producing carbon and magnesium nanomaterials, but rather amore general process and enabling oxidation-reduction reaction forbeneficial formation of nanomaterial in a vapor-nucleation process. Theprocess has been found to be a repeatable process for production ofnanomaterial including, but not limited to, the reaction products.Moreover, the absence of MgO in the reaction product that was treatedwith deionized water and HCl shows that the carbon nanoproduct can beeffectively separated from the MgO nanoproduct by means of a relativelysimple water and acid treatment.

When supplemental, low-pressure, gaseous CO₂ was injected into thecavity in the dry ice to enhance the reaction, there was a significantincrease in the percentage of carbon produced relative to the percentageof MgO. Chemical analysis has shown the reaction products to beextremely consistent from batch to batch even when conditions are variedas discussed above and to consist of nanocarbon graphenes, nano MgO, andcomposites consisting of intercalated layers of graphene and MgO.

Example 2

A reactor was constructed from blocks of solid CO₂, or dry ice, whichwere approximately 12 inches square and 1¾ inches square. A cavityhaving a diameter of approximately 1⅝″ was drilled into one of theblocks to serve as the reactor chamber. Exhaust pressure release ventshaving a diameter on the order of ¼ inch were drilled laterally from theouter edges of the block to the cavity. The second block was used as alid for the reactor.

Magnesium bar stock believed to have a purity of 99% was machined intoseveral batches of various sized flakes. Approximately 10 grams ofmagnesium chips of between number 5 and number 10 sieve mesh (2.00-4.00mm) were placed in the cavity. The flakes were ignited with anoxygen-hydrogen torch and the dry ice lid was immediately place on thelower block. The reaction was observed to be extremely vigorousproducing a sizable amount of light and resulting in some ejection ofwhite smoky (MgO) material from the edges of the two blocks. Thereaction took less than 30 seconds. A residue of agglomerated powderyblack (C) and white (MgO) reaction product material was left in thereactor cavity. The reaction product material was removed by invertingthe dry ice slab and dropping the reaction product into a cleancontainer.

The reaction product was then processed to isolate the carbon materialand provide samples for analysis. The material was separated using 4M (4moles per liter) HCl, which caused the MgO to go into solution as MgCl₂.A black material (carbon) remained and was isolated and removed bywashing the material through a 1 micron filter with alternatingapplications of ethanol and distilled water. The cleaned sample wasspattered onto a plastic sheet, left to dry overnight, then placed in aclean container. A second sample was prepared in a similar manner.

During this study, it was observed that certain sized magnesium chipswere more readily combustible than others and that the reaction productdiffered dramatically in appearance depending on the size of magnesiumchips. Magnesium flakes having a sieve mesh size between number 5 (4 mm)and number 10 (2 mm) resulted in the most complete combustion. Theseparticles were large enough to combust, yet small enough to allow areasonable mass quantity in the reaction.

The samples were analyzed by a number of tests, including TransmissionElectron Microscopy (TEM), Scanning Electron Microscopy (SEM), GlowDischarge Mass Spectrometry (GDMS) and X-Ray Diffraction (XRD).

The TEM and SEM analyses showed that particles from the samples setappeared to be agglomerated, plate-like particles of approximately 10 to60 nanometer scale and had very large surface area. Graphitic carbon wasidentified in the samples by the presence of lattice fringes as well aselectron diffraction (graphitic ribboning). This material appeared to beunique. Crystalline MgO (Periclase) having a particle size in the rangeof 40 to 60 nanometers was clearly observable, and the TEM imageryshowed the presence of MgAl₂O₄ spinels in the form of 40 nanometerpill-like structures.

The GDMS analysis was performed to examine the purity of the samples. Itshowed that the sample material contained 15% magnesium by weight and,somewhat surprisingly, that it also contained 5.1% aluminum by weight.The aluminum was clearly present in the nanospinels and may have been inthe samples in uncombusted form. The only potential source of aluminumwas the magnesium bar stock that was thought to be pure.

The XRD test showed a strong presence of three types of crystallinestructures, with spinels (MgAl₂O₄ nanocrystals) being the dominant form.

From this example, it was determined that the Mg—CO₂ reaction reliablyproduces nanomaterial of carbon and non-carbon types, and thatessentially pure MgO is ejected by the reaction when vents are providedin the reaction vessel. It also demonstrated that the process will formnanomaterial from other reactive feedstock such as aluminum, and thatthe reaction and the vapor-nucleation cycle is likely to convert most,if not virtually all, materials present to nanomaterial form.

This example also demonstrated that the reaction can be controlled, e.g.by altering the magnesium feedstock to affect the efficiency ofcombustion and the composition of the reaction product. This stronglysuggested that the morphology and characteristics of the reactionproducts are controllable.

It also confirmed that significant separation of the reaction productsis feasible. The carbon reaction product was separated by means ofsimple deionized water, alcohol and acid washing, and these steps werefound to be highly effective in reducing the presence of magnesium oxidein the carbon reaction product from its theoretical output ratio ofapproximately 85% MgO and 15% C to approximately 25% MgO and 75% C.

Example 3

Magnesium barstock was machined into chips ranging in size between about2.0 and 4.0 mm (sieve mesh sizes #5-#10). These chips combusted with CO₂in a manner similar to that in Example 2, and two samples were preparedfor separation processing.

As an initial step in the post reaction separation processing, theheterogeneous product samples were ground to a 140 mesh size to reduceagglomeration and provide more uniform samples with greater surface areafor fluid treatment. The ground up samples were introduced into a vesselcontaining deionized water and were processed ultrasonically at 20 kHzand 500 Watts for a defined period of time to further reduce particlesize and increase surface area. Thereafter, 12M (moles per liter) HClwas added to dissolve the MgO reaction product as well as any remaininguncombusted Mg. The HCl reacted with MgO and Mg to form MgCl₂ in anexothermic reaction. The vessel was allowed to cool, following which thesample was treated with HCl again and then once again treatedultrasonically for an identical period of time. Following the secondultrasound treatment, the sample was once again treated with deionizedwater. After these steps, the carbon product was removed by filtration(1 micron) as in Example 2. Two separate batches were prepared in thismanner.

GDMS analysis of the samples showed a substantially lower magnesiumcontent than in Example 2, with 12% by weight in the first sample and11% in the second.

It also revealed the presence of 5.5% aluminum by weight in the firstsample and 3.1% in the second. The magnesium barstock used as thefeedstock was then analyzed and found to contain 2.5% aluminum byweight.

TEM and SEM analysis showed that the two product samples were identicalin physical form and that both samples contained graphitic carbon, whichwas identified by the presence of lattice fringes and electrondiffraction consistent with graphitic material. The size of the carbonparticles was predominantly on the order of 10 to 20 nanometers,substantially smaller than the particles produced in Example 2. Theseparticles were also significantly less agglomerated than the particlesin Example 2. The morphology of the nanocarbon was flat, with irregularedges, and the particles appeared to consist of one to several layers.

XRD analysis showed strong evidence of thin layers of graphitic graphenematerial in both samples, and both samples had two non-graphiticdominant phases: MgAl₂O₄ (spinel) and MgO (periclase). This analysisalso suggested the presence of composited material in addition to thespinel and periclase structures. It also revealed the presence of tracesof pyrolitic carbon, probably from the ignition source. The carbonmaterial in the samples was determined to be hydrophobic.

Porosity tests showed the carbon product sample material to bemesoporous (pores in the range of 1 to 50 nanometers), with a majorityof the pores in the range of 1 to 20 nanometers. Surface area testsshowed surface areas between 230 and 460 square meters per gram. It isbelieved that some pores may be blocked by the Mg—Al oxides (spinels)that were found in the samples.

These tests show that the invention produces one to a few layers of ananocarbon material having a surface area, pore size, pore volume andorder characteristics consistent with high quality graphenes. Theproduct samples were consistent in appearance and test results frombatch to batch.

The GDMS tests indicated that magnesium oxide remained present in thesamples in significant quantities, and the XRD tests provided a strongindication that the magnesium oxide is present as crystallinenano-periclase. Analysis of the TEM images and other tests suggests thatthe remaining MgO is intercalated with the carbon graphene layers. Thisis consistent with the evidence of composite material indicated by theXRD tests. The MgO intercalated with graphene may be an important andnovel material.

The presence of composites consisting of graphenes and MgO in theproduct samples suggests that the production of composites of grapheneor MgO with other non-feedstock materials is also feasible.

Example 4

Laboratory grade, 99.9% pure, magnesium bar stock was machined to theestablished chip size, and an airtight reaction chamber was constructed.Several samples were prepared and tested.

A first sample was prepared by reacting the 99.9% pure magnesium withCO₂ in an argon environment. The reaction product was separated andstored in an argon environment, with the separation process includingHCl, deionized H₂O, and ultrasonic treatment as in Example 3.

A second sample was prepared in a similar manner by reacting the 99.9%pure magnesium with CO₂ in an argon environment, but then a reflux/leachprocess was used to separate the reaction product. The sample wasrefluxed with nitric acid by boiling the sample in the acid andre-condensing vapors in a confined environment. The sample was thenextracted from the solution, cleaned with deionized water, and driedovernight in an oven.

A third sample was prepared by reacting 95% pure magnesium (similar toAZ31) with CO₂ in an argon environment. This sample was not processedfor separation or tested, but instead was stored in an argon environmentfor reference purposes.

A sample of the unreacted laboratory grade (99.9% pure) magnesiumfeedstock was kept in an air environment for the purpose of verificationof the purity of the magnesium input.

In addition, samples of ejected MgO were collected in a vacuum systemattached to the reactor.

The samples were analyzed in a number of tests, including TEM and SEM,GDMS, XRD, pore size, pore volume, surface area, BET, gas sorption, andthermal and oxidation stability.

The GDMS analysis showed that the sample separated by HCl, deionizedH₂O, and ultrasonic processing contained 20% magnesium by weight,whereas the sample separated by the nitric acid reflux/leach processcontained 40% magnesium by weight. It also confirmed the high purity(99.9%) of the magnesium reactant and determined that the MgO sample wasof unusually high purity (above 99%), with none of the contaminantscommonly found in MgO samples.

The XRD tests showed that the sample separated by HCl, deionized H₂O,and ultrasonic processing had only two phases, a dominant crystallineMgO phase and a crystalline carbon phase consistent with graphenes.

The TEM images were very similar in Examples 3 and 4. As can be seen inthe TEM image in FIG. 18, the product contains graphene platelets 173,cubic MgO crystals (periclase) 174, and graphene-MgO composites 176. Thegraphene platelets appear as clear, irregular bodies and include singlelayer graphenes as well as graphenes having several layers. The MgOcrystals are darker, indicating denser or layered material, and have alength of approximately 20 nanometers on each side. The graphene-MgOcomposites have one or more layers of graphene platelets formed on thefaces of the cubic MgO crystals. A single MgO crystal 177 with graphenelayers 178 produced in accordance with the invention can be seen in theTEM image of FIG. 19.

Cubic crystals of MgO, or periclase, produced by the invention can beseen in the TEM image of FIG. 20, where crystals 179, 181, 182 have alength of approximately 30-50 nanometers on each side and crystals havea length of approximately 20 nanometers per side.

The SEM images were also similar to the ones in Example 3 in showingagglomerated material. As can be seen in the SEM image of the samplematerial shown in FIG. 21, the graphene platelets have short-range orderand are on the order of 10 to 20 nanometers in length. The graphene-MgOcomposite material seen in this image has both short- and long-rangeorder, 6 or more layers, and is consistently in the range of 40 to 60nanometers.

In the gas sorption tests, the sample separated by HCl, deionized H₂O,and ultrasonic processing was found to have both a significantly largersurface area and significantly more pore volume than the sampleseparated by the nitric acid reflux/leach process.

In the thermal testing, no melting point of the product was found in thetemperature range tested, and very high thermal transference wasindicated.

The pore testing showed that the majority of the pores have size of 5nanometers, similar to that of the product samples in Example 3. Theyalso showed that they were mesoporous, with pores in the range of 2 to50 nanometers.

The results of the surface area, pore volume, pore size test aresummarized in the table below.

TABLE 2 SURFACE AREA DATA Multipoint BET 2.048E+01 m²/g BJH MethodCumulative Adsorption Surface Area 5.659E+01 m²/g DH Method CumulativeAdsorption Surface Area 5.786E+01 m²/g DR Method Micro Pore Area2.441E+01 m²/g PORE VOLUME DATA BJH Method Cumulative Adsorption PoreVolume 5.141E−02 cc/g BJH Interpolated Cumulative Adsorption Pore5.141E−02 cc/g Volume for pores in the range of 5000.0 to 0.0 Å DiameterDH Method Cumulative Adsorption Pore Volume 5.024E−02 cc/g DR MethodMicro Pore Volume 8.695E−03 cc/g PORE SIZE DATA BJH Method AdsorptionPore Diameter (Mode) 7.005E+00 Å DH Method Adsorption Pore Diameter(Mode) 7.005E+00 Å DR Method Micro Pore Width 2.151E+01 Å

The MgO sample was reacted and functionalized with deionized water toform magnesium hydroxide (Mg(OH)₂), a so-called green plastics fireretardant well known to those skilled in the art. The Mg(OH)₂ functionsas a fire retardant by converting back to MgO and H₂O when exposed totemperatures in excess of 332° C., at which temperature it undergoes anendothermic decomposition. The formation and decomposition of thefunctionalized MgO was verified in a series of successful tests.

This testing confirms that the invention consistently produces graphenesand indicates that graphene is the dominant nanostructure in the productsamples. The thermal test results show very high thermal transferenceconsistent with graphenes, and comparative analysis with available TEMgraphene images shows that the carbon nanostructures are graphenes.Moreover, TEM images from Examples 2-4 showing both lattice fringes andelectron diffraction indicate that the process of the invention producesgraphenes and is extremely consistent over time.

The graphene-MgO composites produced by the invention are believed to benovel, with the graphenes encapsulating the MgO in such a way that thecomposite is inert to acid treatments.

The presence of novel nano-structures, composites, spinels, periclasesand graphenes in the reaction product indicates that the invention canproduce novel materials and composites, depending on feedstock.

This testing also confirms that the invention is controllable such thatthe products can be determined, separated and purified, and themorphologies and attributes of the products can be controlled. Thecombination of XRD and GDMS data indicates that, when the inputs arepure Mg and CO₂, the reaction produces a pure material consisting of MgOand carbon and that all other components were insubstantial. Varying theseparation protocol has been found to have a significant influence onthe purity and character of the product materials. The use of HCl andultrasonification proved to be superior to the use of a nitric acidreflux/leach process for separation of magnesium products from thesample batch. The absence of aluminum in the product samples producedfrom 99.9% pure magnesium confirms that different nanoscale materialscan be produced with different feedstock.

The TEM image of FIG. 18 shows the broad range of capabilities of theinvention. As noted above, it shows graphene platelets 173, cubic MgOcrystals (periclase) 174, and graphene-MgO composites 176. It alsoappears to show some amorphous carbon that could have formed if localconditions in the reactor did not produce adequate reaction heat tofully vaporize the carbon and produce graphenes. This, however, is theonly image of amorphous material obtained in the three phases of testingto date.

Both the sample prepared by HCl and ultrasonic separation and the sampleprepared by the nitric acid reflux/leaching had a larger surface areaand more pore volume than the samples in Examples 2 and 3, possibly dueto the elimination of spinel structures that may have clogged the porespace of the material. This finding is further indication that thereaction process can be manipulated to produce nanomaterials havingsignificantly different characteristics.

The argon environment in the reactor and storing the product samples inargon had no discernable impact on either the reaction process or thereaction products of using inert gas to isolate the reaction wasdetected.

Example 5

Two samples were prepared from gaseous CO₂ in a carbon steel reactionvessel. The first was prepared in a high pressure, pure CO₂ environment,and the second was prepared in a pure CO₂ environment at standardatmospheric pressure. The carbon steel reaction vessel had ports forignition, feedstock injection, and MgO ejection, and Ignition wasprovided by electric arc. Both samples were prepared from magnesiumchips having a size on the order of 2.0-4.0 mm (#5-#10 sieve mesh). Postreaction separation was done with HCl and ultrasound, and the sampleswere dried to create a graphene powder.

Additional samples were prepared in a similar manner but with highpressure gaseous carbon monoxide (CO) in a carbon steel vessel.

The sample prepared from the gaseous CO₂ reaction at high pressure wasexamined with GDMS, TEM, SEM, and XRD testing. The GDMS testing showedthat the percentage of magnesium in the sample was only 10% by weight,whereas the samples prepared with solid CO₂ in the previous examplescontained 20%-25% Mg by weight. The TEM and SEM images both revealedthat the morphology of the materials produced in the reaction wassimilar to that produced from solid (dry ice) CO₂, and the XRD imagesrevealed only one dominant phase—a carbon phase.

The material produced from gaseous CO₂ at atmospheric pressure wasexamined with GDMS and Instrumental Gas Analysis (IGA). The GDMS testingindicated that the mass percentage of magnesium in the samples was 14%by weight, and IGA testing found concentrations of the followingelements by weight percent: nitrogen 0.64%, hydrogen 0.77%, and oxygen8.6%. In comparison, samples prepared with solid CO₂ (dry ice) in theprevious examples contained 11.7% oxygen after processing in fluid withno heat processing and only one processing cycle. TEM analysis showedthe presence of graphene material substantially similar in character andappearance to that shown in the TEM results in Example 4 and the priorexamples.

In preparing the samples with CO, it was found that ignition of thereaction with high pressure CO was extremely difficult and, whensuccessful, resulted in only partial combustion of the magnesium.

Gaseous CO₂ was found to be highly effective as a feedstock in theMg—CO₂ reaction. Virtually all MgO remaining in the samples wasintercalated MgO encapsulated in graphenes that are recalcitrant to HCland ultrasonic purification treatment, and gaseous CO₂ was found toproduce significantly less recalcitrant intercalated MgO than solid CO₂feedstock. The Mg in reaction product is predominantly in the form ofMgO. The MgO weight of the sample prepared with high pressure CO₂ gaswas approximately 14% versus approximately 35% for the samples preparedwith dry ice in the earlier examples.

Gaseous CO₂ at higher pressure also results in significantly lowerrecalcitrant intercalated MgO—C composites in the reaction product thanproducts prepared with gaseous CO₂ at atmospheric pressure. The MgOweight in the high pressure sample was approximately 14% compared withapproximately 20% in the sample prepared at atmospheric pressure.

Highly pure MgO was ejected very vigorously from the reaction chamber,whereas virtually all the graphenes remained within the chamber. Thedegree of such separation can be controlled in a number of ways,including the use of vents and vacuum to recover the MgO and varying theinitial phase and pressure of the CO₂ input.

Carbon monoxide (CO) has been found to be considerably more difficult toreact with magnesium and may not be an attractive alternative to CO₂ inthe reaction. The difficulty in reacting is believed to be due to thelesser amount of oxygen in CO than in CO₂ at similar pressures. CO is,however, believed to be very likely to be very effective in modulatingthe vigor of the Mg—CO₂ reaction.

The invention has been found to be extremely consistent in producingreaction nanoproduct when the CO₂ feedstock is changed from solid CO₂(dry ice) to gaseous CO₂, both at atmospheric pressure and at highpressure. The amount of intercalated MgO-graphene composites has beenfound to be highly controllable by adjustment of the CO₂ feedstock, withgaseous CO₂ at high pressure producing the least intercalated materialand solid CO₂ (dry ice) producing more than 100% more by weight.

It is believed that two operational parameters are responsible for thereduction in the amount of intercalated MgO-graphene composites. First,the saturation of CO₂ at the reaction site is the highest with highpressure gaseous CO₂ and the lowest with solid CO₂ (dry ice), whichsuggests that CO₂ saturation is a critical factor in controlling thedegree of formation of intercalated material. Second, the open spacesurrounding the magnesium in the carbon steel vessels is approximatelyten times the open space in the dry ice blocks. The additional spaceprovides the vaporous reaction product substantially more opportunity tonucleate and form homogenous carbon and MgO nanoparticles. Thus, it isbelieved that a continuous flow system in which the reaction productsare ejected from the reaction site and have the maximum opportunity tonucleate and form homogenous carbon and magnesium oxide nanoparticleswill result in a very low amount of intercalated MgO-graphenecomposites.

Example 6

Samples were prepared in the airtight reaction chamber of Example 4,with a CO₂ flood being used instead of argon to prevent post-reactioncarbon combustion. A partial vacuum and collection receptacle wasattached to the reaction chamber for collecting vented MgO, and solidCO₂ (dry ice) was used as the feedstock in order to provide the maximumamount of intercalated MgO-graphene composite for testing purposes.

A first sample underwent standard fluid and ultrasound processingfollowed by heat treatment at 1200° C. for a period of 2 hours. Thiscycle was repeated twice. Heating was performed in a quartz tube atvacuum, with the material in an alumina boat. GDMS testing showed thefollowing weight concentrations of elements in the sample:

Mg 6% Al 4% Si 7% Ti 0.1% And IGA testing showed the presence of 6.2% oxygen. Thus, the heattreatment significantly reduced the mass quantity of both magnesium andoxygen in the product. The aluminum in the sample is believed to havecome from the alumina boat that held the sample during the heatingprocess.

A second sample was prepared in a similar manner except the material wasplaced in a seasoned quartz boat, the heating was done in a seasonedquartz tube at vacuum, and the heating cycle was repeated three times.GDMS testing showed this sample contained 3% magnesium and 5% silicon byweight, with negligible aluminum and titanium. IGA testing showed thepresence of 3.6% oxygen. Thus, using a quartz boat instead of an aluminaboat at high temperatures was found to eliminate the diffusion ofaluminum into the sample, and it was concluded that the high temperatureof the heating process caused silicon to diffuse from the quartz intothe sample.

The next sample was also prepared in a similar manner, with fluid andultrasonic processing followed by heating in a seasoned quartz boat in aseasoned quartz oven at vacuum at 1200° C. for a period of 2 hours. Thiscomplete cycle was repeated three times, then the sample was heated at1000° C. for a period of 2 hours. GDMS testing showed that the samplecontained 2% magnesium and 6% silicon by weight, and IGA testing showedthe presence of 3.4% oxygen and 0.57% nitrogen. TEM images showed thatthe morphology of the graphene material produced in the process wassimilar to that of material produced without heat treatment, although nonano MgO or MgO-graphene composites were observed. SEM images showedthat the morphology of the materials produced in the process was similarto that of materials produced without heat treatment, and XRD imagesshowed the presence of only one dominant phase—a carbon phase. Thesetests seem to confirm that the silicon material was infused from thequartz boat and possibly also the quartz vacuum apparatus, and it wasconcluded that 1200° C. is an upper boundary for the heating if asilicon-free material is desired.

Another sample was then prepared in a similar manner, with heating in aseasoned quartz boat in a seasoned quartz tube at vacuum at 1000° C. fora period of 4 hours. This cycle was repeated four times. GDMS testingshowed that this sample contained 8.5% magnesium and 0.15% silicon byweight, and IGA testing showed the presence of 4.6% oxygen. Thus,lowering the heating temperature from 1200° C. to 1000° C. significantlyreduced and essentially eliminated the mass quantity of silicon thatdiffused into the sample, notwithstanding the doubling of the heatingtime for all heat cycles. However, the lower heating temperature wasconsiderably less effective in removing oxygen from the sample even withthe increased heating time. Therefore, it was concluded that 1000° C. isa lower boundary for the heating process.

The next sample was prepared in a similar manner, with heating in aseasoned quartz boat in a seasoned quartz tube at vacuum at 1000° C. fora period of 4 hours. This cycle was repeated four times. The sample wasthen heated at 1150° C. for a period of 2 hours, followed by withheating at 1125° C. for a period of 2 hours. GDMS testing showed thatthis sample contained 5% magnesium and 0.1% silicon by weight, and IGAtesting showed the presence of 4.6% oxygen by weight. Thus, with theadditional heating cycle, the quantity of both magnesium and oxygen wasreduced, and the quantity of silicon remained substantially the same.

Another sample was prepared in a similar manner, with a first heatingcycle of 2 hours at 1125° C. followed by four successive cycles ofheating at 1150° C. for 2 hours. The heating was done in a seasonedquartz tube at vacuum, with the material in a seasoned quartz boat. GDMStesting showed that this sample contained 3.5% magnesium and 0.3%silicon by weight, and IGA testing showed the presence of 2.2% oxygen.

A final sample was prepared using five heating cycles at 1150° C. for 2hours each. The heating was done in a seasoned quartz tube at vacuum,with the material in a seasoned quartz boat. GDMS testing showed thatthis sample contained 3.2% magnesium by weight and negligible silicon,and IGA testing showed the presence of 2.1% oxygen. From this, it wasconcluded that 1150° C. is an optimal temperature both for reduction ofthe mass concentration of oxygen and Mg in the sample and for preventingdiffusion of silicon into the graphene sample from quartz equipment.

Although an Ellington diagram showing the relationship betweentemperature and standard free energies in the formation of oxidessuggests a somewhat higher temperature (1850° C.), by doing the heatprocessing under vacuum and for a longer period of time, the inventorshave avoided the need for the higher temperature. However, the highertemperature can be utilized, if desired, with corresponding adjustmentsin pressure and/or processing time, and since reaction rates for manyreactions double with each 10° C. rise in temperature, highertemperatures can have a dramatic effect on the reactions.

Graphene Production

In one presently preferred embodiment of a batch process for producinggraphenes which roughly parallels the embodiment of FIG. 2, the Mg—CO₂reaction is carried out in graphite crucibles placed in a steel vessel.The steel vessel has an internal CO₂ atmosphere around the graphitecrucible to prevent combustion of the graphite and contamination byother gases such as air. The CO₂ is introduced into the vessel at lowpressure and enters the graphite crucible through openings in thebottom, top and sides of the crucible. Magnesium metal chips are placedin the crucible and ignited by an electric arc (40 VAC, 90 A).

The system can have a negative pressure MgO collection system with a 1micron filter attached to the top of the steel vessel, or the MgO can becollected in a low pressure, cooled cylindrical axial collector that hasan auger system to constantly remove the MgO powder that is producedwhen the MgO gas nucleates inside the MgO collector. The MgO iscollected at the exit of the collector and stored for recycling backinto Mg metal or for use in other applications.

The combustion products formed in the graphite crucibles are ground to a140 mesh size (0.104×0.104 mm) to make the material easier to process insubsequent fluid purification processing steps.

The ground material is ultrasonically processed in deionized water. Theprocessing time is dependent on the level of the ultrasonic energyinput, with lower energy requiring longer processing times and higherenergy requiring shorter processing times. The processing can be done,for example, in 2 hour cycles in a 500 watt ultrasonic unit. Sinceenergy is the product of time and power, either time or power can beadjusted as needed. For industrial scale production, large ultrasonicprocessors will be utilized.

Hydrochloric acid (HCL) having a density of 20° Baumé is added to thematerial from the ultrasonic processor to dissolve any free Mg metal andMgO present in the solution, and this new solution is also processedultrasonically for a suitable time at a suitable energy level, e.g. 2hours at 500 watts.

The solution is then filtered in a Büchner vacuum funnel 26 with 2.5micron filter paper, with the graphenes being deposited onto the filterpaper and the MgCl₂ passing through. The filter paper and graphenes arethen heated, in a low temperature oven (less than 100° C.) to dry thegraphenes and facilitate their removal from the filter paper.

The dried material is placed in a seasoned quartz boat in a hightemperature seasoned quartz oven and heated to 1150° C. for a presetperiod of time which can range from less than 2 hours to more than 6hours, depending upon the result desired. The oven is regulated by a PIDcontroller that provides a low temperature ramp up, operation at theprocessing temperature for the preset period of time, and then a rampdown in temperature. The low temperature ramp up stabilizes thecombusted material and drives off any water that may be present in it inorder to avoid any loss of material due to violent evaporation of waterin the material and eruption of the material out of the boat by thewater evaporation energy.

The material is removed from the oven, and a GDMS analysis is made todetermine whether additional processing is required to achieve thedesired level of purity. If so, some or all of the steps in the processcan be repeated until the desired purity is achieved.

This process has been found to be fully reproducible and quite robust inthat unintended or unplanned events in the procedure had no effect onthe final graphene product. For example, prior to the use of the PIDcontrollers, the heating cycles were not exact and varied by as much as+/−30 minutes, and the thermocouples for the temperature controllerswere not certified by a standards laboratory. The procedure is veryforgiving.

If desired, other techniques can be employed to purify the materialbefore the treatment with acid and ultrasound. Ore beneficiation usingdensity separation is effective since there is a significant differencein density between Mg and MgO. Separation can likewise be done bycentrifugal action in a cyclone type of separator.

Ignition Systems

The Mg—CO₂ reaction must be ignited by an external source of heat,preferably one that avoids contamination of the graphene reactionproduct. Many ignition systems have been tested. An H₂/O₂ torch, forexample, has been found to be effective in an open cavity in a sheet ofsolid CO₂ (dry ice), and an H₂/O₂ torch ignited by an electric spark(15,000 volts) has been found to be effective in a gaseous CO₂ vesseloperating in the batch mode. When the reaction is conducted with CO₂ atatmospheric pressure, it was found to be preferable to use an AC or DCelectric arc, with a ground connection to the graphite crucible and thearc being struck with a magnesium rod or carbon electrode in very closeproximity to the magnesium chips.

With the electrode and the ground in a Siamese parallel configurationand the two simultaneously coming very close to, but not touching themagnesium chips, the system has the potential to ignite the Mg/CO₂mixture in an aerosol environment.

If desired, a high intensity lamp, a glow plug, or an H₂/O₂ torch can beused in place of the electric arc to ignite the Mg/CO₂ mixture. However,an electric arc can be left on continuously to insure continuouscombustion of the Mg/CO₂ mixture, and multiple carbon arc units can alsobe used to insure complete and total combustion of the Mg/mixture.

Reactor Design

Different materials have been tested for use in the construction of areactor for carrying out the invention. A carbon steel reactor performedwell initially but degraded from repeated exposure to high temperature.The reactor shown in FIG. 8, with a pocket of high temperature zirconiaoxide (ZrO₂) in the base, worked well thermally, but contaminated thereaction products with ZrO₂. A graphite reactor with a graphite crucibleperformed very well over extended testing, and graphite is currently thepreferred material for reaction containment. Graphite has good hightemperature properties, and any contamination carbon from the graphitewill just go into the graphenes. Also, graphite is readily machined todesired shape and dimensions.

Heat Cycle Containment

Heating the carbon reaction products to the temperatures employed in theseparation and purification stages requires that the samples be treatedunder vacuum to prevent combustion of the carbon, and it also requiresthat the oven be made of materials that are capable of maintaining theirstructure over repeated exposure to the processing temperatures withoutcontaminating the products being treated. Quartz tubes and mullite orporcelainite tubes (3Al₂O₃2SiO₂ or 2Al₂O₃SiO₂) have been usedsuccessfully for this purpose. Other materials, such as titanium, havebeen found to fail structurally and to contaminate the product.

Observations and Conclusions

The invention produces materials that are remarkably consistent overtime and with different embodiments. TEM and XRD results demonstrateconsistent production of graphenes of a highly crystalline nature. Poresize and volume measurements also remain consistent, with graphenes fromwhich MgO-graphene composites are removed having significantly highersurface area than graphenes from which the composites are not removed.

The reaction products can be controlled and managed at various stages ofthe process. The addition of heat treatment to the fluid and ultrasoundsteps results in a substantial reduction of recalcitrant intercalatedMgO-graphene composites due to the release of oxygen from the MgO bondor by sublimation of the MgO in the graphene composite. The temperatureand duration of the heat treatment can be determined empirically, or itcan be calculated through the use of Ellinghams Diagram. The reductionof MgO-graphene composites takes place in a linear manner where eachheat cycle reduces the remaining composites by a constant percentage,and it is believed that the reaction product graphenes can be purifiedcommercially to a purity level of 99% or higher. In order to have theleast amount of intercalated MgO-graphene composites to start with, itis preferable to use gaseous CO₂ feedstock, even more preferablypressurized gaseous CO₂ feedstock, rather than solid CO₂ (dry ice)feedstock.

The examples show that the beneficial vapor-nucleation cycle and thebeneficial exothermic oxidation-reduction reaction of CO₂ and Mg areparts of a broader, more general process that can produce nanomaterialsother than graphenes and other carbon nanoproducts. The process createsa vaporized homogeneous material that “self-reorganizes” as purematerials to a significant degree.

Highly pure MgO reaction product is beneficially ejected from thereaction site, e.g. through vents in the reaction chamber and can, forexample, be collected in a vacuum particle collector. The MgO ejectioncan also be utilized as a preliminary step in separating the reactionproducts.

Batch processing of magnesium metal and solid CO₂ (dry ice) in theproduction of graphenes results in a product with a relatively highinitial concentration of MgO, which is believed to be the result ofincomplete combustion due to insufficient CO₂ to combine with themagnesium. When gaseous CO₂ is added to the reaction, there is asignificant decrease in the amount of MgO in the product, thusdemonstrating that the composition of the reaction product can becontrolled by controlling the amount of CO₂ available to the reaction.

Although the Mg—CO₂ reaction is the preferred method of generating thehigh temperatures required in the production of graphenes and othernanoproducts, it is possible to use other materials in the reaction, ifdesired. Thus, for example, aluminum can be used instead of magnesium asa primary feedstock to make graphenes and/or graphene composites withdifferent chemical and physical compositions. There are other elementsthat could also be considered for use as reactants in the process, andthere likewise are other carbon compounds, such as CH₄ and otherhydrocarbons that could be used instead of CO₂ to provide the carbonsource for the reactions.

The purity and composition of the reaction feedstock can also affect thepurity of the reaction products and the composition of the finalproduct. Thus, for example, if the magnesium feedstock has even a smallpercentage of aluminum in it, the reaction will produce aluminum andspinel contamination in the graphene produce. Likewise, CO₂ purity willaffect the final chemical composition of the reaction products. The hightemperature reactions and use of various reactants, additives, orcomponents may make it possible for many chemical applications to bedone on a continuous industrial scale when heretofore they could only bedone on that scale with a solar furnace.

By including other gases in the CO₂ mixture, the addition of otherelements to the graphene can be easily accomplished. For example, theaddition of borane (BH₃ or B₂H₆) to the CO₂ results in a p-dopedgraphene semiconductor when a semiconductor material is doped with thereaction product, and the addition of ammonia (NH₃) to the CO₂ resultsin an n-doped graphene semiconductor when a semiconductor material isdoped with the reaction product. In view of the desirable electronicproperties of graphene, p-doped and n-doped graphene semiconductorscould have wide use and substantial value.

It should be noted that even though the measured reaction temperature of5610° F. (3098° C.) is below the vapor point of MgO (6512° F./3600° C.),MgO nanoparticles are nevertheless formed by the reaction. The inventorsbelieve this may be due to the temperature deep in the reaction zonebeing substantially higher than the temperature that is measured outsidethat zone.

It also appears that the reaction temperatures at which thenanomaterials are formed may range from about 1000° F. (537° C.) toabout 7000° F. (3871° C.).

The nanomaterials produced by the invention have shown a strong tendencyto form as separate homogeneous particles, with the MgO tending tobeneficially vent and the carbon graphenes tending to remain in thereactor vessel.

The high temperature of the reaction may have industrial applicationbeyond the production of graphenes, nano-periclase or compositesthereof. For example, the energy and temperature of the reaction may beuseful in alloying fine powders of metals such as aluminum, steel, oriron with magnesium and/or in infusing such metals with graphenes toproduce products such as light weight, super strong graphene-steel, amagnetic or field weldable magnesium-iron alloy, or a new family ofiron, aluminum, or steel materials.

The invention has a number of important features and advantages. Itprovides a process for the production of graphenes and othernanomaterials, utilizing a beneficial vapor-nucleation cycle enabled bythe high energy and heat of a highly exothermic oxidation-reductionreaction of magnesium and carbon dioxide, together with integratedfeedstock management, cooling of the reaction products, capture of heatfrom the reaction, recycling of energy and materials produced by thereaction, capture of reaction product, separation and purification ofreactor product, and product functionalization.

The reaction produces extreme temperatures that cause an extraordinarybreakdown of material bonds, most likely in a vapor state, followed by arapid cooling of the vaporized material as it is forced away from thereaction. This results in the vapor contacting an extreme decliningtemperature gradient which causes the material to beneficially nucleateand coalesce into predominantly homogeneous nanomaterial forms.

If desired, other sources of very high temperature, including otheroxidation-reduction reactions involving earth metals and oxygen bearingmolecules, can be utilized instead of the reaction of magnesium andcarbon dioxide to generate the conditions for the process to producenanomaterials.

The invention produces nanomaterials from virtually any material presentin the reaction and exposed to the high energy and temperature of thereaction, and beneficially produces nanocarbon and nano-MgO. In thepreferred mode, these beneficially formed nanomaterials arepredominantly in the form of homogeneous, nanoscale, crystalline formsof carbon known as graphenes and MgO known as periclase.

The invention consistently produces nanomaterials of similar morphologyand character over time, from batch to batch, with different embodimentsof the process, and when the feedstock is altered in form and/orpressure, as can be seen in the TEM images of FIGS. 22 a-22 c. FIGS. 22a and 22 b show samples generated by solid CO2 (dry ice) on 10 and 20nanometer scales, and FIG. 22 c shows a sample generated with gaseousCO2 on a 20 nanometer scale. The samples were produced in batchprocesses over a period of 18 months and treated only with hydrochloricacid (HCl). These images show the remarkable consistency of the graphenemorphology over the 18 month period and among the different embodimentsof the process.

FIGS. 23 a and 23 b show groups of individual graphene platelets 186,187 which were formed on cubical MgO crystalline substrates, as seen,for example, in FIG. 20. After the graphene platelets were formed, theMgO crystals were removed chemically, e.g. by dissolution inhydrochloric acid (HCl), leaving the graphene platelets adhering to eachother on the six sides of a hollow cube.

The invention produces single layer graphenes and graphenes having justa few layers, a valuable nanomaterial with characteristics that areconsidered promising for a significant number of present and futureapplications. The presence and the morphology of graphenes have beenconfirmed by both measured and observed attributes of the material,including appearance, surface area, x-ray reflectivity and porosity areconsistent with graphenes.

The invention also produces nanoscale magnesium oxide crystals, orpericlase. A significant amount of MgO produced by the reaction can bebeneficially vented and captured. The measured purity of captured MgOproduced by the invention is 99.2%, which is among the highest levels ofpurity produced. Such very pure nano MgO may have significantapplications in a number of fields, including medicine, electronics andcomputing, food, and fire safety. This MgO is highly suitable to be usedfor recycling to magnesium for reuse in the reaction of the invention.The MgO can be functionalized as a fire retardant for plastics by simplereaction with water to form Mg(OH)₂.

The invention can also produce unique and potentially valuablecombinations of nanomaterials such as intercalated graphene-MgOcomposites and nano spinels. The graphene-MgO composite materials arebelieved to be novel materials, and nano spinels are relativelyuncommon. Any material present in the reaction is likely to be reducedto nanomaterial form as long as it is a solid at ambient temperature.

The invention has been found to be highly controllable and scalable. Thefeedstock and other material and gaseous inputs can be varied in size,pressure and chemical composition. This will produce varied andcontrollable results, including novel materials, composites, andnon-carbon, non-magnesium nanomaterials.

The reaction itself can be regulated or controlled by means such asalteration in the type, nature, morphology, amount, or pressure of thefeedstock, injection of inert gases, cooling or pre-heating of theinjected materials, type of ignition, and type and size of vessel. Thiswill produce varied and controllable results.

The reaction products can also be controlled. The inputs to thereaction, the energy and temperature of reaction, and other parameterscan be manipulated to control the nature, constituency and type ofreaction products. Due to the high energy and temperature of thereaction, the reaction may provide way to alter the quantum mechanicalattributes of the graphenes and other reaction products, including lowelectrical resistivity, high electrical conductivity, and/or themagnetic fields issued from the material. The post-reaction processesfor treatment, separation, and purification of the material can bemanaged and controlled to produce varied and controllable products, andintercalated MgO-graphene composites can be reduced or eliminated by theaddition of a heat cycle to the purification and separation process.

The invention is scalable and adaptable. The reaction is simple andinherently energetic, producing the energy and temperature required toproduce the desired nanomaterials. The feedstock is common and readilyavailable, and the reaction can be contained with known materials andmethods. Energy and materials capture and reuse can also be done withknown materials and methods. A number of standard, well-known separationprocesses and methods can be employed and optimized, and the inventionprovides a novel separation process involving beneficial ejection ofMgO. The reaction products are consistent, controllable, andpredictable, and the invention can be implemented at different scalesand in different forms, ranging from large-scale nanomaterialsproduction to mobile emissions capture. The MgO reaction product can bebeneficially captured and efficiently recycled for reuse as magnesiumfeedstock for the reaction process, thereby avoiding the impact oflarge-scale operation of the invention on global demand, supply, andprice of magnesium.

The invention provides a novel, unique, general, complete and scalableprocess for production of nanomaterials, including graphenes, whichovercomes obstacles that have heretofore prevented the production ofcarbon nanomaterials from reaching commercial scale and price pointssuitable for the many industries interested in using such materials toimprove their products and solutions.

Previously known methods and strategies for the production of graphenesare not amenable to scaling and cost reduction. Known nanocarbonproduction processes are energy, materials and labor intensive. They arereliant on mineral or synthetic graphite feedstock. However, the supplyof graphite is not elastic, and high quality crystalline graphite, thepreferred source material for graphene production, is in limited supply.The energy required for many nanomaterials production processes aresignificant, with known processes using large amounts of mechanicaland/or electrical energy.

Known nanocarbon production processes are difficult to scale. Many ofthem are difficult to automate and require costly specialized equipmentthat would be challenging to scale. While processes for producing carbonnanotubes have been widely known for more than ten years and promises toscale and lower price points to reasonable levels have been made, theproduction of carbon nanoproducts is no closer to industrial scale andprice than it was ten years ago.

The invention does not rely on graphite or relatively scarce highlycrystalline graphite feedstock, but rather on carbon dioxide, a widelyavailable, low cost gas for the production of carbon nanomaterial orgraphenes. It utilizes a highly exothermic and beneficial reaction thatdoes not require energy to produce carbon nanomaterial or graphenes.While some energy is used in separating and purifying the reactionproducts, substantially less energy is used overall by the inventionthan by other processes, and the energy footprint of the invention couldeven approach zero. The invention recycles important materials,including the magnesium feedstock and hydrochloric acid used inseparation and purification of the reaction products. The simplicity andvigor of the reaction enable the invention to be scaled to produce verylarge volumes of graphenes. The low cost of carbon dioxide feedstock,the ability to recycle magnesium feedstock, and the relatively simpleseparation and purification protocol make it possible to producegraphenes at exceptionally low cost, well below the most optimisticestimates for known processes and roughly equivalent to market pricesfor high quality micron-scale graphite powders of comparable purity.

The invention can be implemented in various embodiments, each of whichbenefits from the unique integrated features and function of theinvention and can be utilized to achieve specific objectives. Continuousflow embodiments generally will produce substantially greater volumes ofgraphenes and other nanomaterials than batch processes, but batchprocess can be utilized if more precise control and manipulation of thegraphene product or customized composite materials are desired. A batchprocess with gaseous CO₂ is the most controllable process fordetermination of processing variables and allows the graphene materialcharacteristics to be altered readily. The batch process is similar tothe “pot lines” used in electrolytic aluminum reduction and in theelectric furnace production in steel production. The batch process isalso valuable at the development stage for determining systemoperational parameters.

The modular embodiment can be utilized in the capture and destruction ofCO₂ and particulates in fixed base or large mobile fossil fuelcombustion systems. Also, since MgO is known to perform as a CO₂ captureagent, the nano MgO reaction product may be useful in enhancing theperformance of an MgO-based CO₂ capture system.

The invention has significant advantages for the industrial productionof nanomaterials, including scalability, cost, and product quality, e.g.consistency, reliability, and purity. The products of the invention havesignificant applicability to advanced industrial products, solutions andapplications. Graphenes have unique and proven capabilities inelectrochemistry and other applications, including catalytics,magnetics, heat and mass transfer, semiconductors, hydrogen storage andadvanced materials construction. The ultra pure nano MgO produced by theinvention has numerous potential applications in many industries,including the plastics industry, in addition to its use as feedstock forrecycled Mg for reuse in the invention. Other nanomaterials that can bereadily produced by the invention may also be valuable. Nano Spinels,for example, have application in lithium ion battery cathodes, and nanoMgO may be important as a base constituent in CO₂ capture.

The invention provides significant control of the inputs as well as thereaction and separation processes. By varying the inputs, temperature,speed, constituents, and other parameters of the reaction and thepost-reaction separation process, the morphology, constituency andquantum mechanical attributes of the nano-carbon and other nanoproductscan be controlled.

It is apparent from the foregoing that a new and improved process forthe production of graphenes and other nanomaterials has been provided.While only certain presently preferred embodiments have been describedin detail, as will be apparent to those familiar with the art, certainchanges and modifications can be made without departing from the scopeof the invention as defined by the following claims.

The invention claimed is:
 1. A composition of matter comprisingmagnesium oxide (MgO) nanocrystals and carbon nanoparticles which form acomposite material with the MgO nanocrystals.
 2. The composition ofclaim 1 wherein the carbon nanoparticles and the MgO nanocrystals areintercalated in the composite material.
 3. A composition of mattercomprising magnesium oxide (MgO) nanocrystals and graphene plateletsthat adhere to each other and to the faces of the MgO nanocrystals. 4.The composition of claim 3 wherein the MgO nanocrystals are cubic.